2008 January – Nar Nar Goon – Carney St (Victoria) – E.coli

Nar Nar Goon – (Victoria) – E.coli

The seventh E. coli detection in a routine sample was in Carney Street, Nar Nar Goon, in the Tynong locality, on 31 January 2008 (50 E. coli organisms per 100mL) with a relatively high free chlorine residual of 0.2mg/L. The sampling point is within the Tynong distribution zone which
is supplied from Cardinia Reservoir via Tyabb Reservoir. Secondary disinfection occurs at Tyabb and Tynong Reservoirs to maintain a chlorine residual of 0.7mg/L of water leaving the reservoir. All system checks were clear and a re-sample at the same customer sample tap and samples at four nearby taps, taken on the following day, were clear of E. coli.

Escherichia coli should not be detected in any 100 mL sample of drinking water. If detected
in drinking water, immediate action should be taken including investigation of potential
sources of faecal contamination.

“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.

Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG 2011